The Giro d'Italia appears locked up by the incredible Tadej Pogačar after his dazzling time trial triumph, but Australian Ben O'Connor has made a dramatic move into fourth place overall.

On a superb day for the Australians, O'Connor's compatriot Luke Plapp also impressed in the seventh stage, moving to fifth following the 40.6-kilometre race against the clock between Foligno and Perugia.

But they were just support acts to yet another glorious solo display from Slovenian Pogačar, who won his second stage in six days to move two minutes and 36 seconds ahead of Colombian Dani Martinez in the general classification standings.

Pogačar's latest demonstration of superiority on a route that culminated in a tough six-kilometre ascent means that before the first week of the three is even over, the remarkable 25-year-old Giro debutant already seems sure to prevail, barring a calamity.

"After the world championships last year, today was my first race on the TT (time trial) bike again," he said.

"I started a bit with an easier pace and had to get used to the TT bike and then I paced myself until the climb and then went full gas so I'm super happy with today.

"I knew the climb suited me and that was my advantage especially as it was quite steep."

Ineos Grenadiers' Italian time trial ace Filippo Ganna had looked on course for victory after clocking 52:01 and Pogačar was still behind after the second intermediate checkpoint.

But he made light of the climb to Perugia to cross the line 17 seconds quicker in 51:44.

It earned him huge gains over his nearest pursuers after starting the day 46 seconds clear.

O'Connor finished 11th place on the stage, 2:07 slower than Pogačar, but it was enough to elevate him seven places to fourth in the general classifciation standings, just 47 seconds behind third-placed Geraint Thomas.

It helped make up for a trying start to the Giro for the 28-year-old Decathlon AG2R La Mondiale rider.

Team Jayco AlUla's Plapp, who was seventh quickest in the time trial, moved up to within nine seconds of O'Connor and grabbed the white jersey as the race's leading young rider.

"A super nice day," Plapp said.

"I haven't had the best TTs in Europe since I started my professional career, so I'm happy. The white jersey too. It's a perfect first week of the Grand Tour for me."

Pogačar will doubtless try to pile on the pressure further as the race hits the high mountains in the punishing eighth stage, which ends with a brutal climb of more than 14km to Prato di Tivo after the 152km grind from Spoleto.

AAP